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ABSTRACT: Carbon monoxide (CO) has been shown to have remarkable therapeutic value at low dosage by suppressing inflammation via inhibitory effects on macrophages, which are also precursors of osteoclasts (OC). The objective of the present study was to determine whether CO limits bone loss through its effects on osteoclastogenesis. Intraperitoneal injection of CO-releasing molecule 2 (CORM2) into mice with reduced bone mass due to ovariectomy (OVX) resulted in significantly elevated bone mass. Increased serum levels of collagen-type I fragments, tartrate-resistant acid phosphatase 5b, and reactive oxygen species (ROS) due to OVX were also decreased when treated with CORM2. In vitro, CORM2 inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced OC formation without affecting bone resorption. CORM2 reduced long-lasting ROS levels and nuclear factor-κB (NF-κB) activation in response to RANKL. Inhibition of NADPH oxidase partially reduced the inhibitory effect of CO. CO induced increase of peroxiredoxin 1 (PRX1) in BMM. Down-regulation of PRX1 reduced the inhibitory effect of CO on OC formation and sustained the ROS levels induced by RANKL, suggesting that CO reduces generation of ROS and scavenges ROS to inhibit osteoclastogenesis. These data suggest that the inhibitory effect of CO on osteoclastogenesis is caused by impaired RANKL signaling through defective NF-κB activation and reduced levels of long-lasting ROS. These changes result in decreased bone loss. Our data highlight the potential utility of CO for ameliorating bone loss induced by loss of ovarian function.
Biochemical pharmacology 02/2013; · 4.25 Impact Factor
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ABSTRACT: The aim of the present study was to evaluate the effect of fibrinogen on number and function of osteoclast (OC), consequently resulting in bone loss. It was hypothesized that the enhanced level of released fibrinogen due to loss of ovarian function caused bone loss by acting on OCs. Bone loss was induced by ovariectomy (OVX) in mice and analyzed by microCT. The effect of fibrinogen on OCs was evaluated by tartrate-resistant acid phosphatase, annexin V, and actin staining, pit formation observed on dentine slices and western blotting. Exogenous fibrinogen increased OC survival, actin ring formation, and bone resorption in vitro. The effect of fibrinogen was dependent on β3 integrin, which is a marker for mature OCs. Fibrinogen induced the activation of transforming oncogene from Ak strain (Akt), Ras-related C3 botulinum toxin substrate 1 (Rac1), and Rho family of GTPase (Rho) and the degradation of the Bcl-2 interacting mediator of cell death (Bim) in a manner similar to macrophage-colony stimulating factor (M-CSF). OVX increased plasma fibrinogen and serum M-CSF together with elevated actin ring formation and bone loss. The increased fibrinogen level due to loss of ovarian function may contribute, at least partly, to bone loss through the enhanced number and activity of OCs.
AJP Endocrinology and Metabolism 09/2012; · 4.75 Impact Factor
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ABSTRACT: Herpes virus entry mediator (HVEM), which is constitutively expressed at a high level on myeloid lineage cells, is also expressed on bone marrow-derived macrophages, suggesting that it may play a role in bone metabolism by affecting osteoclasts (OC) derived from bone marrow-derived macrophages. To address this question, we evaluated bone mass by micro-computed tomography and the number and activity of OC by tartrate-resistant acid phosphatase (TRAP) and pit formation on dentine slices, comparing HVEM-knockout mice with wild-type mice. The absence of HVEM led to a higher bone mass and to decreased levels of serum collagen type I fragments and serum TRACP5b in vivo. In vitro HVEM deficiency resulted in a reduced number and activity of OC and an impaired receptor activator of nuclear factor-κB ligand signaling through reduced activation of nuclear factor-κB and of nuclear factor of activated T-cells cytoplasmic 1. Exogenous soluble HVEM decreased expression of TRAP, whereas soluble LIGHT (a ligand of HVEM) increased it, indicating the occurrence of a positive signaling through HVEM during osteoclastogenesis. Our findings indicate that HVEM regulates bone remodeling via action on OC. The higher bone mass in the femurs of HVEM-knockout mice could be, at least in part, due to attenuated osteoclastogenesis and bone resorption resulting from decreased receptor activator of nuclear factor-κB ligand signaling in the OC.
Endocrinology 08/2012; 153(10):4808-17. · 4.46 Impact Factor
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ABSTRACT: Platinum nanoparticles (PtNP) exhibit remarkable antioxidant activity. There is growing evidence concerning a positive relationship between oxidative stress and bone loss, suggesting that PtNP could protect against bone loss by modulating oxidative stress. Intragastric administration of PtNP reduced ovariectomy (OVX)- induced bone loss with a decreased level of activity and number of osteoclast (OC) in vivo. PtNP inhibited OC formation by impairing the receptor activator of nuclear factor-κB ligand (RANKL) signaling. This impairment was due to a decreased activation of nuclear factor-κB and a reduced level of nuclear factor in activated T-cells, cytoplasmic 1 (NFAT2). PtNP lowered RANKL-induced long lasting reactive oxygen species as well as intracellular concentrations of Ca(2+) oscillation. Our data clearly highlight the potential of PtNP for the amelioration of bone loss after estrogen deficiency by attenuated OC formation.
Experimental and Molecular Medicine 04/2012; 44(7):432-9. · 2.48 Impact Factor
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ABSTRACT: Monocyte chemoattractant protein-1 (MCP-1) is associated with various inflammatory diseases involving bone loss, and is expressed along with its receptor by bone marrow-derived macrophages (BMM), which are osteoclast (OC) precursors. To investigate the role of MCP-1 in bone remodeling, we compared MCP-1-knockout (KO) mice with wild-type (WT) mice. The absence of MCP-1 increased bone mass and lowered serum collagen type I fragments (CTX-1) and TRACP 5b, but had no significant effect on the N-terminal propeptide of type I procollagen, suggesting that OCs are primarily responsible for the bone phenotype observed in the absence of MCP-1. MCP-1 deficiency resulted in reduced numbers and activity of OCs in vitro. It also led to a reduced level of c-Fms and receptor activator of nuclear factor-κB receptor and impaired actin ring formation. Activation of ERK, Akt, Rac1, and Rho upon M-CSF stimulation was also reduced and our evidence suggests that the aberrant actin ring formation was partly due to reduced activation of these molecules. Our findings point to a role of osteoclast MCP-1 in regulating bone remodeling. The higher bone mass in the femurs of MCP-1-KO mice could be, at least in part, due to decreased osteoclastogenesis and bone resorption resulting from aberrant M-CSF signaling in OCs.
Journal of Cellular Physiology 06/2011; 227(4):1619-27. · 3.87 Impact Factor
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ABSTRACT: Previous work has suggested that the LIGHT-TR2 costimulatory pathway plays a role in the acute and chronic stages of dextran sulfate sodium (DSS)-induced colitis [Steinberg et al. (2008); Wang et al. (2005)]. To clarify the role of TNFR-related 2 (TR2) signaling in the maintenance of intestinal homeostasis, we generated a TR2 knock-out (KO) mouse. Using DSS to induce colitis, we compared the colitic symptoms and pathological changes in wild type (WT) and TR2 KO mice, and the production of cytokines by the diseased colons. We also studied the role of TR2 in suppressing innate and adaptive immunity in the DSS model. TR2 deficient mice were characterized by reduced symptoms of intestinal inflammation compared with wild-type mice, and reduced production of cytokines. We therefore generated a monoclonal antibody against mouse TR2 which was specific to TR2 and capable of blocking TR2 signals. With this antibody, we demonstrated that antagonizing TR2 during the development of DSS-induced colitis reduced the symptoms of inflammation. Our findings suggest that TR2 is an important mediator in colitis, and may serve as a therapeutic target in inflammatory bowel disease.
Molecules and Cells 01/2011; 31(2):99-104. · 2.18 Impact Factor
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ABSTRACT: Tumor necrosis factor receptor-related 2 (TR2, HVEM or TNFRSF-14) plays an important role in immune responses, however, the mechanisms regulating its expression are unclear. To understand the control of TR2 gene expression, we studied the upstream region of the gene. Gel supershift assays revealed inducible binding of nuclear factor of activated T cells (NFAT) to a putative NFAT site within the TR2 promoter. Furthermore, cotransfection of a dominant negative NFAT construct, or siRNA for NFAT, resulted in increased expression of a TR2 reporter gene. Our findings demonstrate that NFAT negatively regulates TR2 expression in activated T cells.
Experimental and Molecular Medicine 12/2010; 42(12):805-10. · 2.48 Impact Factor
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ABSTRACT: TR2 (TNFR-related 2, HVEM, or TNFRSF-14), a member of the TNFR family, is involved in a number of immune responses. While TR2 is expressed on the surface of T cells during the resting state, little is known regarding how expression of the TR2 gene is regulated. To understand the mechanisms regulating the expression of TR2 in T cells, we analyzed the 5' flanking region of TR2. We identified an important region for the activity of the TR2 promoter using site directed mutagenesis. Using EMSA analysis, we found that IRF-2 was bound to the promoter region of the TR2 gene during the resting state of EL-4 T cells. Transfection of IRF-2 expression plasmid and of dominant negative IRF-2 mutant further confirmed our results. Together, these data demonstrate that IRF-2 is involved in the regulation of TR2 expression in EL-4 T cells.
Biochemical and Biophysical Research Communications 04/2008; 367(2):277-83. · 2.48 Impact Factor
